The overall objectives for this project remain three-fold: to construct a detailed electrical equivalent circuit model for the plasma membrane of Neurospora, to develop kinetic models for each of the major ion transport systems in that membrane, and to identify the major control systems which modulate transport in relation to energy metabolism. The first two objectives are now being approached by a systematic comparison of current-voltage curve data (on the principal proton efflux pump, and on a proton-coupled glucose uptake system) with a newly-developed generalized kinetic model for electrogenic ion transport systems. In addition, new experiments will examine the relationship between the kinetics of current flow through the proton pump and variations of intracellular pH (measured with glass microelectrodes). At least temporarily, the investigation of possible control systems--by which metabolism modulates transport--has come to focus on the interdependence of membrane potential, levels of cyclic AMP, and turgor pressure.